One
of the most extraordinary objects in the Milky Way galaxy is
Sagittarius A* (pronounced Sagittarius A star). This small object is a
bright source of radio waves in the constellation of Sagittarius that
was discovered in 1974.
Since then, astronomers have
made numerous observations of Sagittarius A* and the stars nearby, some
of which orbit it at very high velocity. That implies that Sagittarius
A* is extremely massive and since it is so small it must also be hugely
dense.
That’s why many astronomers believe this object
is a supermassive black hole lying at the centre of the galaxy. In
fact, Sagittarius A* is about 4 million times more massive than the Sun
packed into a volume not much bigger than the solar system.
But
there is another explanation—that this massive dense object is a
wormhole that connects our region of space to another point in the
universe or even to another part of the multiverse. (Astrophysicists
have long known that wormholes are allowed by the laws of general
relativity and may well have formed soon after the Big Bang.)
And
that raises an interesting question. If Sagittarius A* is a wormhole,
how can astronomers distinguish it from a black hole? Today, we get an
answer thanks to the work of Zilong Li and Cosimo Bambi at Fudan
University in Shanghai.
These guys have calculated
that plasma orbiting a black hole would look different to the same
plasma orbiting a wormhole. They have calculated the difference and even
simulated the resulting images that should be possible to collect using
the next generation of interferometric telescopes. In other words, if
there is a wormhole at the center of our galaxy, we should be up to see
it within the next few years.
The
idea that a wormhole might exist at the centre of the galaxy is not as
far-fetched as it sounds. In the early universe, quantum fluctuations
may well have a connected different regions of the cosmos, creating
wormholes that were preserved during inflation when universe increased
in size by many orders of magnitude.
The presence of a
wormhole would actually solve a major problem of galaxy formation. In
recent years, astronomers have observed what appear to be supermassive
black holes at the centre of many galaxies. Indeed, many believe that
supermassive black holes are necessary for galaxies to form in the first
place— they provide the gravitational pull to hold galaxies together in
their early stages.
But if that’s true, how do
supermassive black holes become so massive so quickly? After all, the
one at the centre of our galaxy must have been in place about 100
million years after the Big Bang. That doesn’t leave much time to grow.
A
wormhole, on the other hand, is a primordial object formed in the blink
of an eye after creation. So if wormholes did form in this way, they
would be present in the early universe to trigger the formation of the
first galaxies.
That’s
why telling one from the other is so significant— the difference
provides important clues about the nature of the early universe.
On
the face of it, it’s easy to imagine that telling them apart ought to
be impossible. After all, both black holes and wormholes sit behind an
event horizon from which light cannot escape. There is no way of seeing
what’s going on inside an event horizon.
However,
there is an important difference between black holes and wormholes— the
latter is much smaller than the former and this is the basis on which
Zilong and Bambi say they can be told apart.
They
consider a cloud of hot plasma orbiting each body and emitting infrared
light. They then calculate the trajectory the light must take to escape
towards Earth where it can be imaged.
Because this
light has difficulty escaping from the extreme gravitational fields of
these objects, the image of the cloud of plasma becomes smeared out. But
the difference in size between a black hole and a wormhole causes a
crucial difference in this smearing. This distinctive pattern of
smearing is the signature that astronomers can use to tell them apart.
Nobody
has succeeded in viewing Sagittarius A* in the optical or near infrared
part of the spectrum. But that is going to change in the next few
years.
In particular, astronomers are building an
infrared interferometer called GRAVITY at the Very Large Telescope
Interferometer in the Atacama desert of northern Chile. This device will
be capable of resolving clouds of plasma around Sagittarius A*and
spotting the unique signature of a wormhole, if one is there.
These
images will provide a fascinating insight into the nature of the
massive dense object at the centre of our galaxy. The confirmation that
it is a supermassive black hole will be important but the discovery that
it is a wormhole will be mind-blowing.
GRAVITY
is being shipped to Chile next year and will hopefully be in operation
soon after that. If there is a wormhole at the heart of the Milky Way,
the likelihood is that we’ll find out in the not too distant future.
Ref: arxiv.org/abs/1405.1883 : Distinguishing Black Holes And Wormholes With Orbiting Hot Spots
No comments:
Post a Comment